#include<stdio.h>
int main()
{
   int N,i;
   scanf("%d",&N);
   double zi,mu,sum;
   zi=2;
    mu=1;
   sum = 0;
for(i=1;i<=N;i++)
{
    double a=zi/mu;
    sum=sum+a;
    zi=mu+zi;
    mu=zi-mu;
}
printf("%.2lf",sum);




}
